a)Technical Field of the Invention
The present invention relates to an improved structure of the main shaft of an umbrella.
b) Description of the Prior Art
FIG. 1 shows a conventional collapsible, large size umbrella comprising a main shaft A1 and an auxiliary extension shaft A2. The bottom section of the main shaft A1 is provided with a positioning elastic ball A11 which positions the extension shaft A2 at the position hole A21 after the main shaft A1 is inserted thereto. The rotating eccentric pressing shaft A3 at the top end of the extension shaft A2 is used to mount the main shaft A1 to the extension shaft A2. The eccentric pressing shaft A3 is urged by a press shaft A31 to eccentrically secure with the extension shaft A2. Loosening the press shaft A31 causes the main shaft A1 to disengage from the extension shaft A2 and the umbrella structure can be unloaded.
The drawbacks of the conventional collapsible umbrella are as follows:
1) As the conventional umbrella requires two parts for combination to form the entire umbrella, the manufacturing of elements is complicated. As a result, unnecessary cost of production will occur. PA1 2) As a result of the two independent parts of the umbrella, it is possible that one of the parts may be displaced, and the umbrella cannot be used. PA1 3) Due to the weight of the umbrella, it is rather troublesome to assemble the two independent parts under strong wind environment PA1 4) The rotating eccentric pressing shaft A3 provides insufficient stress and therefore, connection of the main shaft A1 and the extension shaft A2 by urging is weak, and the umbrella may fall down as a result of accidental impact. PA1 5) After a long period of use of the umbrella, the main shaft A1 may be dented, and the urging by the rotating eccentric pressing shaft A3 is weak. PA1 6) The dented main shaft A1 of the umbrella may be eroded in due course.